Android自动伸展动画,Android Expand/collapse animation(展开收起动画)

//展开

public static void expand(final View v) {

int matchParentMeasureSpec = View.MeasureSpec.makeMeasureSpec(((View) v.getParent()).getWidth(), View.MeasureSpec.EXACTLY);

int wrapContentMeasureSpec = View.MeasureSpec.makeMeasureSpec(0, View.MeasureSpec.UNSPECIFIED);

v.measure(matchParentMeasureSpec, wrapContentMeasureSpec);

final int targetHeight = v.getMeasuredHeight();

// Older versions of android (pre API 21) cancel animations for views with a height of 0.

v.getLayoutParams().height = 1;

v.setVisibility(View.VISIBLE);

Animation a = new Animation()

{

@Override

protected void applyTransformation(float interpolatedTime, Transformation t) {

v.getLayoutParams().height = interpolatedTime == 1

? LayoutParams.WRAP_CONTENT

: (int)(targetHeight * interpolatedTime);

v.requestLayout();

}

@Override

public boolean willChangeBounds() {

return true;

}

};

// Expansion speed of 1dp/ms

a.setDuration((int)(targetHeight / v.getContext().getResources().getDisplayMetrics().density));

v.startAnimation(a);

}

//收起

public static void collapse(final View v) {

final int initialHeight = v.getMeasuredHeight();

Animation a = new Animation()

{

@Override

protected void applyTransformation(float interpolatedTime, Transformation t) {

if(interpolatedTime == 1){

v.setVisibility(View.GONE);

}else{

v.getLayoutParams().height = initialHeight - (int)(initialHeight * interpolatedTime);

v.requestLayout();

}

}

@Override

public boolean willChangeBounds() {

return true;

}

};

// Collapse speed of 1dp/ms

a.setDuration((int)(initialHeight / v.getContext().getResources().getDisplayMetrics().density));

v.startAnimation(a);

}